The sand rat (Psammomys obesus) will be used to study some of the characteristics of the diabetes mellitus like syndrome that can be induced by diets of high caloric content. Breeding of diabetes resistant and susceptible strains will be carried out, and the animals used to identify factors controlling insulin-secretion using isolated islet cell preparations. Attempts will be made to purify enough insulin to permit amino acid analysis. The predisposition of sand rats to infection will also be studied, with special attention being given to the role of white blood cells.